Integrating top-down and scenario-based methods for constructing software specifications

How to achieve a complete and consistent software specification by construction is an important issue for software quality assurance but still remains an open problem. The difficulty lies in the fact that the assurance of the completeness needs user’s judgments and the specification keeps changing as requirements analysis progresses. To allow the user to easily make such judgments and to reduce chances for creating inconsistencies due to frequent specification modifications, in this paper we describe an intuitive, formal, and expressive specification method that integrates top-down decompositional and scenario-based compositional methods. The decompositional method is used at an informal level with the goal of achieving a complete coverage of the user’s functional requirements, while the compositional method is used to precisely define the functionality of each scenario and to construct complex scenarios by composition of simple scenarios in a formal, intuitive language called SOFL. Combination of the decompositional and compositional processes can facilitate the analyst in completing a specification in a hierarchical structure. We present an example to illustrate how the integrated method is used in practice and describe a software support tool for the method.